Characteristic move for the Philidor defense. Black attains a playable albeit passive position.

White immediately strikes at black's centre threatning 4.dxe5 then if 4...dxe5 5.Qxd8+ Kxd8 6.Nxe5 where black can't castle, has lost a pawn and is faced with 7.Nxf7+ This is unacceptable for black.

Plausible but this gives up the centre too easily. White gets a free hand in the centre. 3...Nd7 to keep the tension in the center may have been played as an alternative.

Not 4.Qxd4 because of 4...Nc3

A commendable developing move. Brings a piece out, attacks something and controls a part of the centre.

Most economical way to defend the threatened e pawn.

Good defensive move which facilitates early castling.

White develops his bishop to an active post and also gets ready to castle. So far, play has been rational by both sides with no glaring mistakes. White aims to completely dominate the centre and use his extra pawns on the king side to promulgate a king side attack. However, milder moves such as 6.Be2 may have been played.

?! This move is correct strategically but the timing is wrong. Part of black's strategy should be to expand on the queenside where he has more pawns but that comes later after development is complete. Better alternatives where O-O or Nbd7 or Nc6. The text move has the further drawback that it allows white to activate his pieces. White's Knight is attacked. Where should it go??

First to try to exchange off black's bishop which has a fine diagonal.